Magnetic valve for controlling an injection valve of an internal combustion engine

ABSTRACT

A solenoid valve is described, its armature having a part that is slidingly displaceable on the foundation bolt and is movable between two stops of the foundation bolt against the tension force of a restoring spring. When the armature strikes the valve seat of the solenoid valve, the slidingly displaceable part moves further under the influence of its inertial mass on the foundation bolt in the closing direction against the tension force of the restoring spring, until it strikes the second stop of the foundation bolt. The resulting transfer of momentum to the foundation bolt reduces impact of the armature on the valve seat and causes the armature to more quickly reach a defined rest position in which the solenoid valve is closed.

BACKGROUND INFORMATION

[0001] The present invention relates to a solenoid valve for controllinga fuel injector for an internal combustion engine according to thepreamble of claim 1.

[0002] Such a solenoid valve, which is known from German PatentApplication 196 50 865 A1, is used to control the fuel pressure in thecontrol pressure space of a fuel injector, e.g., an injector of a commonrail injection system, where the fuel pressure in the control pressurespace in turn controls the movement of a valve member, so that aninjection opening of the injector may be opened or closed. The knownsolenoid valve has an electromagnet situated in a housing part andhaving a coil and a magnetic core, a movable armature and a controlvalve element that is moved with the armature and is acted upon by aclosing spring in the closing direction, this control valve elementcooperating with a valve seat of the solenoid valve and thus controllingthe flow of fuel out of the control pressure space. In the case of thesolenoid valve known from German Patent Application 196 50 865 A1, thearmature is designed in two parts having a foundation bolt and a anchorplate in a slidingly displaceable mount on the foundation bolt. Inaddition, however, there are also known solenoid valves for controllinginjectors, the foundation bolt being fixedly connected to the anchorplate.

[0003] One disadvantage of the known solenoid valves is armaturerebound. When the magnet is shut down, the control valve element, whichis secured to the armature, is accelerated suddenly toward the valveseat by the closing spring to close a fuel outflow channel out of thecontrol pressure space. The impact of the control valve element on thevalve seat may result in vibration and/or rebound of the control valveelement, which is a disadvantage and has a negative impact on theinjection operation. In the case of the solenoid valve having a two-partarmature, which is known from German Patent Application 196 50 865 A1,rebound is prevented by the fact that the anchor plate is displaceableon the foundation bolt and is moved further against the tension force ofa restoring spring in impact of the control valve element on the valveseat. The effectively braked mass thus becomes smaller. However, then itis necessary to prevent post-pulse oscillation of the anchor plate onthe foundation bolt, which would be a disadvantage. This is achieved bya hydraulic damping space formed between a sliding sleeve secured on theanchor plate and a sliding piece situated in a stationary mount on thehousing part of the solenoid valve, damping any post-pulse oscillationof the anchor plate. In the case of a very strong deflection of theanchor plate in the direction of closing of the control valve element,the anchor plate strikes against the sliding piece situated in astationary mount in the housing part. Any residual pulse is transferredto the stationary sliding piece and from there to the housing part.

ADVANTAGES OF THE INVENTION

[0004] The solenoid valve according to the present invention having thecharacterizing features of claim 1 is situated on a slidinglydisplaceable part on the foundation bolt, the part being displaceablebetween two stops, both of which are fixedly situated on the foundationbolt. On impact of the control valve element with the valve seat, theslidingly displaceable part moves in the direction of closing of thecontrol valve element against the tension force of the restoring spring,like the anchor plate in the case of the solenoid valve known from therelated art. The mass of the slidingly displaceable part and the tensionforce of the restoring spring are designed so that the slidinglydisplaceable part strikes against the second stop of the foundationbolt. Since this second stop is not fixedly mounted on the housing, butinstead is movable with the armature and is secured on it, rebound ofthe armature from the valve seat is reduced by the transfer of momentumof the slidingly displaceable part to the foundation bolt. This ispossible because the momentum of the armature rebounding on the valveseat and the momentum of the lagging, displaceable part on thefoundation bolt are directed in opposing directions. The presentinvention may also be used to advantage with such solenoid valves inwhich the anchor plate is designed in one piece with the foundationbolt, thus preventing post-pulse oscillation of the anchor plate. Byreducing the rebound and post-pulse oscillation of the control valveelement on the valve seat, it is advantageously possible to set shorterintervals between preinjection and the main injection, because thearmature takes less time to assume a defined rest position.

[0005] Advantageous embodiments and refinements of the present inventionare made possible through the features characterized in the subclaims.

[0006] The second stop formed on the foundation bolt may be formed toadvantage by a ring surface, facing the slidingly displaceable part, ofa hollow cylindrical sleeve fixedly connected to and displaced on thefoundation bolt. In assembly, the displaceable part is pushed onto thefoundation bolt first and then the sleeve is pushed onto it.

[0007] The first stop opposite the second stop for the displaceable partmay be formed in a simple manner by a ring shoulder on the foundationbolt between the anchor plate and the second stop.

[0008] The slidingly displaceable part advantageously includes asleeve-shaped base body pushed onto the foundation bolt and having onits end facing the first stop a flange on which the restoring spring issupported.

[0009] The fact that the mass of the slidingly displaceable partcorresponds approximately to the mass of the armature formed by theanchor plate and the foundation bolt results in the momentum of thedisplaceable part being approximately the same as that of the armaturerebounding on the valve seat.

[0010] The present invention may be applied with solenoid valves using aone-part armature having a anchor plate secured on the foundation boltor using a two-part armature having a anchor plate displaceable relativeto the foundation bolt. In the latter case, the anchor plate is thenprovided as the slidingly displaceable part which strikes against thesecond stop of the foundation bolt in the closed position of thesolenoid valve.

DRAWINGS

[0011] Embodiments of the present invention are illustrated in thedrawings and explained in the following description.

[0012]FIG. 1 shows a cross section through the top part of a fuelinjector known from the related art and having a solenoid valve;

[0013]FIG. 2 shows a partial cross section through an embodiment of thesolenoid valve according to the present invention having anelectromagnet, an armature, a control valve element and a valve seat.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0014]FIG. 1 shows the top part of a fuel injector 1 known in therelated art, intended for use in a fuel injection system equipped with ahigh-pressure fuel reservoir which is supplied continuously withhigh-pressure fuel through a high-pressure delivery pump. Fuel injector1 shown here has a valve housing 4 having a longitudinal bore 5 in whichis situated a valve piston 6 which works with its one end on a valveneedle situated in a nozzle body (not shown). The valve needle issituated in a pressure space which is supplied with fuel under highpressure through a pressure bore 8. In an opening lifting movement ofvalve piston 6, the valve needle is lifted against the closing force ofa spring by the fuel high pressure acting constantly on a pressureshoulder of the valve needle in the pressure space. Then the fuel isinjected into the combustion chamber of the engine through an injectionopening connected to the pressure space. By lowering valve piston 6, thevalve needle is pushed in the closing direction into the valve seat ofthe fuel injector, and the injection operation is concluded.

[0015] As shown in FIG. 1, on its end facing away from the valve needle,valve piston 6 is guided in a cylinder bore 11 which is provided in avalve piece 12 which is inserted into valve housing 4. In cylinder bore11, end face 13 of valve piston 6 closes a control pressure space 14which is connected by an inlet channel to a high-pressure fuelconnection. The inlet channel is designed in essentially three parts. Abore passing radially through the wall of valve piece 12, its insidewalls forming an inlet throttle on a portion of their length, isconstantly connected to an annular space 16 surrounding the valve piece,this annular space in turn being constantly connected, through a fuelfilter inserted into the inlet channel, to the high-pressure fuelconnection of a connector 9 that may be screwed into valve housing 4.Annular space is sealed by a ring gasket 39 with respect to longitudinalbore 5. Control pressure space 14 is exposed to the high fuel pressureprevailing in the high-pressure fuel reservoir via inlet throttle 15.Coaxially with valve piston 6, a bore running in valve piece 12 branchesoff out of control pressure space 14, forming a fuel outflow channel 17which is provided with an outflow throttle 18 and opens into a reliefspace 19, which is connected to a low-pressure fuel connection 10, whichin turn is connected to a fuel return of injector 1 in a manner notshown further here. The outlet of fuel outflow channel 17 out of valvepiece 12 is in the area of a conically countersunk part 21 of theexterior end face of valve piece 12. Valve piece 12 is fixedly bracedvia a screw element 23 with valve housing 4 in a flange area 22.

[0016] A valve seat 24 with which a control valve element 25 of asolenoid valve 30 controlling the fuel injector cooperates is providedin conical part 21. Control valve element 25 is linked to a two-partarmature in the form of a foundation bolt 27 and a anchor plate 28, thearmature cooperating with an electromagnet 29 of solenoid valve 30.Solenoid valve 30 also includes a housing part 60 which holds theelectromagnet and is fixedly connected to valve housing 4 via screwableconnecting means 7. With the known solenoid valve, anchor plate 28 ismounted so it is dynamically displaceable on foundation bolt 27 underthe influence of its inertia against the prestressing force of arestoring spring 35, and it is pressed by this restoring spring in therest state against a stop ring 26 secured on the foundation bolt. At itsother end, restoring spring 35 is supported fixedly on the housing on aflange 32 of a sliding piece 34 guiding foundation bolt 27, the slidingpiece 34 being fixedly clamped with this flange between a spacer disk 38placed on valve piece 12 and screw element 23 in the valve housing.Foundation bolt 27 and with it armature disk 28 and control valveelement 25 connected to the foundation bolt are constantly acted upon inthe closing direction by a closing spring 31 supported fixedly on thehousing, so that control valve element 25 is normally in contact withvalve seat 24 in the closed position. On energization of theelectromagnet, anchor plate 28 is pulled by the electromagnet, and indoing so, outflow channel 17 is opened toward relief space 19. Betweencontrol valve element 25 and anchor plate 28 there is a ring shoulder 33on foundation bolt 27, this ring shoulder stopping on flange 32 when theelectromagnet is energized and thus limiting the opening lift of controlvalve element 25. Spacer disk 38 is used to adjust the opening liftbetween flange 32 and valve piece 12.

[0017] The opening and closing of the injector is controlled by thesolenoid valve, as described below. Foundation bolt 27 is acted uponconstantly by closing spring 31 in the closing direction, so thatcontrol valve element 25 is in contact with valve seat 24 in the closedposition and control pressure space 14 is closed toward relief side 19,so that a high pressure is very rapidly built up there through the inletchannel and is also applied in the high-pressure fuel reservoir. Overthe area of end face 13, the pressure in control pressure space 14generates a closing force on valve piston 6 and the valve needle whichis connected to it, this closing force being greater than the forcesacting in the opening direction as a result of the applied highpressure. If control pressure space 14 is opened by opening the solenoidvalve toward relief side 19, the pressure in the small volume of controlpressure space 14 drops very rapidly, because the latter is uncoupledfrom the high pressure side via inlet throttle 15. Consequently, theforce acting on the valve needle in the opening direction from the fuelhigh pressure prevailing at the valve needle is predominant, so that itmoves upward and the at least one injection opening is opened for theinjection. However, if solenoid valve 30 closes fuel outflow channel 17,the pressure in control pressure space 14 may be built up again byadditional fuel flowing through inlet channel 15, so that the originalclosing force is applied and the valve needle of the fuel injectorcloses.

[0018] In closing the solenoid valve, closing spring 31 pressesfoundation bolt 27 with control valve element 25 suddenly against valveseat 24. Rebound or post-pulse oscillation of the control valve element,which would have a negative effect, occurs due to the fact that theimpact of the foundation bolt on the valve seat produces an elasticdeformation of the same. This elastic deformation acts as an energystorage mechanism, a portion of the energy in turn being transferred tothe control valve element, which then rebounds away from valve seat 24together with the foundation bolt. The known solenoid valve, which isshown in FIG. 1, therefore uses a two-part armature having a anchorplate 28 uncoupled from foundation bolt 27. Although in this way it ispossible to reduce the total mass striking the valve seat, a post-pulseoscillation of the anchor plate, which would be a disadvantage, must bereduced by a hydraulic damping device between anchor plate 28 andsliding piece 34.

[0019]FIG. 2 shows one embodiment of the solenoid valve according to thepresent invention. The same parts are labeled with the same referencenumbers. The solenoid valve illustrated in FIG. 2 has a one-partarmature in which anchor plate 28 is designed in one piece withfoundation bolt 27. A guide journal 37 which projects away from anchorplate 28 is slidingly displaceable in a recess in electromagnet 29. Aprojection 36 on the anchor plate guarantees a minimum distance betweenthe electromagnet and anchor plate 28 on contacting electromagnet 29.Furthermore, an additional part 50 is provided, including asleeve-shaped base body made of metal on whose one end a flange 52 isformed. Part 50 is situated in a slidingly displaceable manner onfoundation bolt 27 of the armature, the movement of slidinglydisplaceable part 50 on foundation bolt 27 being limited by a first stop43 and a second stop 41. The inside diameter of an opening 51 formed inthe slidingly displaceable part is slightly larger than the outsidediameter of middle section 55 of foundation bolt 27. First stop 43 isformed by a ring shoulder or step of foundation bolt 27. Second stop 41is formed by a ring-shaped surface piece of a hollow cylindrical metalsleeve 40 pushed onto the foundation bolt. End section 53 of foundationbolt 27 facing valve seat 24 has a smaller diameter than center section52 of foundation bolt 27 carrying slidingly displaceable part 50, sothat the two sections form one step 54. In the manufacture of thearmature, first slidingly displaceable part 50 is pushed onto centersection 55 of the foundation bolt and then sleeve 40 is pushed onto endsection 53. When sleeve 40 is pushed onto the foundation bolt, thesleeve comes to rest against step 54 and is secured in this position onthe foundation bolt, which is accomplished by welding, caulking or someother suitable method. As also shown in FIG. 2, a guide disk 45 havingan opening 56 is also provided. Guide disk 45 and a spacer 57 areclamped between a screw element 23 and valve piece 12 in the valvehousing. End section 53 of foundation bolt 27 is provided with controlvalve element 25 and is slidingly displaceably mounted in opening 56 inguide disk 45. A restoring spring 35 is supported at one end on flange52 of slidingly displaceable part 50 and at its other end it issupported on guide disk 45 fixedly on the housing.

[0020] In a position in which the armature is in contact withelectromagnet 29, restoring spring 35 presses slidingly displaceablepart 50 with flange 52 against first stop 43. When the electromagnet isshut down, the armature together with the anchor plate and thefoundation bolt is accelerated by closing spring 31 toward valve seat24. The greater tension force of closing spring 31 counteracts thesmaller tension force of restoring spring 35. As soon as control valveelement 25 strikes the valve seat, slidingly displaceable part 50 movesin the closing direction because of its inertial mass, so the additionalmass of part 50 does not increase the total mass to be decelerated bythe valve seat. Slidingly displaceable part 50 moves on foundation bolt27 against the tension force of restoring spring 35. Shortly after themoment when foundation bolt 27 strikes valve seat 24, lagging, slidinglydisplaceable part 50 strikes stop 41 of foundation bolt 27. In doing so,the momentum of slidingly displaceable part 50 is transferred to thefoundation bolt, so that the momentum of the rebounding armaturedirected in the opposite direction is reduced by the transfer ofmomentum. The mass of the slidingly displaceable part is advantageouslydesigned so that the absolute value of both momentums is the same.Slidingly displaceable part 50 makes it possible to achieve the resultthat the rebounding movement of the armature is prevented or at leastdiminished, and the solenoid valve is closed more reliably. Part 50 thusactively counteracts rebound and/or post-pulse oscillation of thearmature. This advantageously shortens the time required to move controlvalve element 25 into a defined rest position, thus permitting a smallerinterval between preinjection and main injection. Then slidinglydisplaceable part 50 is pushed back by restoring spring 35 into itsstarting position at first stop 43.

[0021] In deviation from the embodiment illustrated here, the armaturemay also be designed in two parts, having a anchor plate slidinglydisplaceably mounted on the foundation bolt. In this case, the anchorplate may be regarded as the slidingly displaceable part which transfersits kinetic energy to the foundation bolt through its impact on thesecond stop of the foundation bolt and thus actively prevents rebound ofthe armature.

What is claimed is:
 1. A solenoid valve for controlling a fuel injectorof an internal combustion engine, the solenoid valve having a housingpart (60), an electromagnet (29), a movable armature having a anchorplate (28) and a foundation bolt (27), a control valve element (25),which moves with the armature, is acted upon by a closing spring (31) inthe closing direction, and cooperates with a valve seat (24) for openingand closing a fuel outflow channel (17) of a control pressure space (14)of fuel injector (1), and a part (28, 50) able to be displaced in asliding manner on the foundation bolt (27) under the influence of itsinertial mass in the closing direction of the control valve element (25)against the tension force of a restoring spring (35), a first end of therestoring spring (35) being situated in a stationary mount on thehousing part (60), and the other end pressing the slidingly displaceablepart against a first stop (26, 43) secured on the foundation bolt (27)against the closing direction of the control valve element (25), whereina second stop (41) is situated on the foundation bolt (27), and at thelatest in the closed position of the solenoid valve when the controlvalve element (25) comes to rest on the valve seat (24), a displacementof the slidingly displaceable part (50) on the foundation bolt (27),resulting from the inertia of its mass and directed against the tensionforce of the restoring spring (35), causes abutment of the slidinglydisplaceable part (50) against the second stop (41) of the foundationbolt (27), so that post-pulse oscillation and/or rebound of the controlvalve element (25) from the valve seat (24) is preventable.
 2. Thesolenoid valve according to claim 1, wherein the second stop (41) isformed by a ring-shaped surface, facing the slidingly displaceable part(50), of a hollow cylindrical sleeve (40) fixedly connected to thefoundation bolt (27).
 3. The solenoid valve according to claim 1,wherein the first stop (51) is formed by a ring shoulder formed on thefoundation bolt (27) between the anchor plate (28) and the second stop(41).
 4. The solenoid valve according to claim 1, wherein the slidinglydisplaceable part (50) has a sleeve-shaped base body connected to thefoundation bolt (27) and having on its end facing the first stop (51) aflange (52) on which the restoring spring (35) is supported.
 5. Thesolenoid valve according to claim 1, wherein the mass of the slidinglydisplaceable part (50) corresponds approximately to the mass of thearmature formed by the anchor plate (28) and the foundation bolt (27).6. The solenoid valve according to one of claims 1 through 5, whereinthe foundation bolt (27) is designed in one piece with the anchor plate(28).
 7. A use of a solenoid valve according to one of claims 1 through6 in a fuel injector in an internal combustion engine.